Lithium cells utilizing sulfuryl chloride or thionyl chloride as the cathode depolarizer are characterized by very high open circuit voltages (OCV). The OCV of the Li/SO.sub.2 Cl.sub.2 cell is 3.90 volt, while that of the Li/SOCl.sub.2 cell is 3.65 volt. These cells consist of an electrode package of a Li foil anode and a porous carbon black cathode, the two being electrically insulated by a fiberglas separator. The SO.sub.2 Cl.sub.2 or SOCl.sub.2 liquid cathode depolarizer, having rendered ionically conductive by dissolving LiAlCl.sub.4 in it, is added to the electrode package contained in a suitable container such as a glass vial or a metal can. The load voltages of the cells are usually high, being only slightly below the open circuit voltage, when discharged at low current densities such as 0.5 to 1 mA/cm.sup.2. For example, a Li/SO.sub.2 Cl.sub.2 D-cell discharged at 0.88 mA/cm.sup.2 has a mid-discharge voltage of about 3.4 V while a Li/SOCl.sub.2 C-cell discharged at 1 mA/cm.sup.2 has a mid-discharge voltage of 3.3 V. However, the load voltages of these cells decrease significantly when discharged at high current densities; for example, 25 mA/cm.sup.2. At these currents, the load voltages of the cells with uncatalyzed cathodes are only about 2.5 V. That is to say, the rate capability of the Li/SOCl.sub.2 and the Li/SO.sub.2 Cl.sub.2 cell is poor. It is desirable to maintain the load voltages of these cells close to their open circuit voltages even at current densities as high as 25 mA/cm.sup.2. It is recognized that the poor rate capability is related to the low activity of the porous carbon cathode.
Some improvement in the rate capability of the carbon cathode has been achieved by adding to the carbon black metals such as platinum (K. Klinedinst, J. Electrochem. Soc., 131, 492 (1984)) or transition metal macrocyclic complexes such as iron phthalocyanine and iron tetraphenyl porphyrin (N. Doddapaneni, U.S. Pat. No.4,613,551). Platinum is very expensive and its addition makes the cell very costly. The metal macrocyclic complexes are not readily available. They are unusual materials and are prepared by tedious procedures. The need exists for catalysts which can be prepared from readily available reagents and are effective in increasing the rate capability of Li/SO.sub.2 Cl.sub.2 and Li/SOCl.sub.2 electrochemical cells.
Accordingly, an object of this invention is to provide catalyzed cathodes, for sulfur oxyhalide cells, which can be readily prepared from common reagents and are effective in significantly increasing the rate capability of the cells.